Offset-printing means



Mar. 3, 1925. 1 1,528,660

M. DE sPr-:RATI

OFFSET PRINTING MEANS Fi1ed May 2e, 1924 Patented Mar. 3, 15'925.

UNITED STATES MARIANO DE SPRATI, 0F TURIN, ITALY.

OFFSET-PRINTING MEANS.

Application led May 26, 1924. Serial No. 716,020.

To all whom it may concern:

`Be it known that I, MARIANO DE .SPERA'rn subject of the King of Italy, residing at Turin, Italy, have invented certain new and useful Improvements in Offset-Printing Means, of which the following is a specification.

The present invention relates to means for producing prints from printing plates, comprising an intermediate or transfer surface on which an inked printing plate produces an image which is then transferred on the paper to be printed.

The present invention has for its object a layer adapted to produce an intermediate or transfer surface for said purpose, which is particularly useful in connection with the printing of photocollographic or gelatin printing plates.

According to the present invention said layer consists of a material containing a colloidal substance, and its operative or transferring surface is treated to be in condition to take ofi' ink from the lprinting plate and transfer it to the paper to be printed, While the underlying portion of said layer is able to absorb and retain moisture and release it gradually to its said surface.

For the use of the layer according to the present invention a printing machine may be used which comprises an intermediate drum between the plate carrying drum and the platen drum.

The ligure of the annexed drawing shows diagrammaticall the essential parts of a machine adapted7 for the use of the layer according to the present invention.

In said figure, 1 is a drum carrying a printing plate 2, and 3 is an intermediate or offset drum carrying a sheet 4 of the material according to the present invention which is hereinafter particularly described.

. The drum 5 is a platen drum carrying the paper or other material to be printed on,`

i5-and adapted to press at the required time inafter described, and 8 is a roller adaptedV to come in contactwith the transfer layer to impart moisture to the same layer or remove moisture from it, as hereinafter described,

.stances as barium sulfate,

Of course the above described arrangement is disclosed merely for the purpose of explanation and the transfer layer according to the present invention may be used in machines of any other appropriate kind.

According to the present invention thez sheet 4 intended to transfer the inked image from the printing plate 2 to the paper sheet is provided with a layer of an emulsion of colloidal substances preferably with added substances as hereinafter described, and said layer has its operative or ink transferring surface somewhat hardened to put it in condition to take olf the ink from the printing plate and to transfer said ink to the paper, while the ortion of said layer underlying said trans er surface reta-ins the property of absorbin and storing moisture, this property bemg peculiar to colloidal sub stances, and is able to deliver said moisture at its transfer surface.

The transfer surface of said layer may be hardened by treating it with an alkaline bichromate bath and by exposing it to the action of light to cause said alkallne bichr0- mate to make hard the exposed skin of the layer; the skin when treated in this manner is able to retain the ink taken off from the printing plate and to deliver it vto the paper or other material to be printed.

The same result may be obtained by treating said layei of colloidal substances in other manners adapted to harden the skin thereof, sa by an alum bath by an alcohol bath, or other hardening substances, orA substances able to improve the property of the layer skin of retaining greasy ink used in printing may be incorporated in the same layer. For 'this purpose may be used starch, gummy materials, or powdered earthy submagnesium oXid and the like.

Hereinafter is disclosed a method for producing and treating a transfer layer according to the present invention.

Ten parts of gelatin of medium hardness are dissolved in water in a 'boiling water bath, and to such a solution is added, While stirring, a solution of 3 parts of Wheat starch in 20 parts of water, and then are added one part of white g ycerin and 0,2 vpart of phenol; the mixture is filtered.

The emulsion thus obtained is spread on a paper sheet which preferably is slightly sized or glued and is ver strong, or on a very tine grain fabric; saicf emulsion is pref- 'ei-*ably spread by mechanical means tofobtain a very uniform layer of about 35/1000 f an intense chromatization of the exposed surface lor skin of said layer is obtained, said chromatization progressively decreasing in the portion of said layer underlying its skin from this skin towards the surface adhering to the supporting sheet. The layer is finally washed and dried.

In use, is located on the oifset or transfer drum 3 of the printing machine, said sheetY being indicated at 4 1n the drawing, `and the pa 7 consisting of a plurality of superimposed sheets of wetted cloth is located between said drum and sheet 4; the sheet 4 may also be wetted in a bath of water containing glycerin before being located on said drum and pad. v

The transfer layer is thus nearly dry on its skin or transfer surface because of the hardening treatment imparted thereto, and

the amount of moisture contained therein progressively portion.

The transfer surface of the layer is thus suiiiciently hard and resistant to receive from the printing plate the whole amount of ink of the image and to apply it to the increases in its underlying paper without being injured from this latter, while the internal moisture may be delivered through said transfer surface by effect of the pressure imposed o n the said layer for printing and inking purposes, and it puts said transfer layer 1n condition to apply the ink to the paper to be printed.

In 4the operation of the machine the several drums and rollers are drivel@ in rotation to cause the printing late 2 to take ink from inking rollers 6 and to deliver,y it to the transfer sheet 4 when contacting therewith, while this transfer sheet on coming in contact with the `paper located on the platen drum 5 applies to the same the ink it has taken oi from ysaid printing plate 2 and produces on the paper the requisite ima T: roller 8 is adapted to contact with the sheet 4 located on druml 3 and provides for removing moisture from sheet 4 should' this sheet and its transfer layer contain a much too large amount of molsture, or said roller` may be used to im art additional moisture to said layer if desired. This provisison for intermittentlyA wetting the transfer layer surface instead of wetting the printing plate 2 makes it possible to treat photocollographic plates 4in the same manner as lithographie plates.

Hereinafter are given other compositions the sheet provided with said layer l layer according to the present invention.

Parts by weight Water 100 Medium hardness gelatin 9 Barium sulfate 2 Glycerin x. 1 Phenol 0,2 II.

Water 100 Fish glue 10 Gamboge gum 2 Glycerin 1 III.

Water 100 Medium hardness gelatin f 10 Magnesium oxid 2 lycerin 1 Phenol 0,2 fIv. ,A Water 100 Medium hardness gelatin 10 Barium sulfate 3 Glycerin 2 Phenol 02 described.

The described mixtures may be spread on a paper sheet or on a sheet of a water-pervious or water-impervious fabric, and may be put on the market in a condition in which they may be easily utilized.

It is also advisable to cause the operative surface of the transfer layer to be more or less grained or matted by pouring the mixture on a suitably grained or matted surface or by embedding therein grains of a substance, as powdered pumice stone, metal powders, or the like; a similar result may also be obtained in the case of a layer made hard by treatment with alkaline bichromate and light, by locatin a net in front of the skin of said layer efore exposing it to light, said net being adapted to cause the light to'act to different extents in the difierent Aportions of the skin.

Of course the present invention is not restricted to the operations and mixtures above referred to, and the said mixtures may be modified or combined with each other and the described hardening and other treatments may be used in respect of the several mixtures for improving the operation of the transfer layer without de artin from the scope of the present invention as ereinafter claimed.

What I claim as my invention and desire to secure by United States Letters Patent 1s 1. Transfer means for offset printing, embodying a layer of a material which comprises a colloidal substance; such layer havin its skin treated to render it capable ofta ingA ink and transferring itfto the surface to be printed, the underlying portion of said layer eing adapted to retain moisture applied atthe back and release it at said skin. 2. Transfer means for offset printing, embodying a layer of a material which comprises a colloidal substance; such layer having its skin treated to render it hard so as to take ink and transfer it to the surface to be printed, the underlying portion of said layer beingpervious to moisture applied at the back and adapted to release it at said skin.

3. Transfer means for offset printing, em-

bodying a layer of a material which comprisesl 4a colloidal substance; such layer having its skin treated to render it hard so as to take ink and transfer it to the surface to be printed, the underlying portion of said layer being pervious to moisture applied at the back to a progressively decreasing extent starting from said skin.

4. Transfer means for offset printing, embodying a layer of a material which comprises acolloidal substance; such layer having its skin sensitized by an alkaline bichromate and exposed to light, whereby said skin is renderedhard so as to take ink and transfer it to the surface to be printed, the underlying portion of said layer being adapted to retain moisture applied atl theback and release it at said skin.

5. Transfer means vfor offset printing, ern-v bodying a layer of a material which comprises gelatin; such layer having its skin sensitized by an alkaline bichromate and exposed to light, whereby said skin is rendered hard so as to take ink and transfer it to the surface to be printed, the underlying portion of said layer being adapted to retain moisture' applied at the back and release it at said skm.

6. Transfer'means for ofset printing, embodying a layer ofa material which comprises a colloidal substance and glycerin; such layer having its skin treated to render it hard so as to take ink and transfer it to the. surface to be printed, the underlying portion of said layer being pervious to moisture and adapted to release it at said skin.

7. Transfer means for offset printing, embodying a layer of a material which comprises a colloidal substance and gummy substances; such layer having its skin treated to render it hard so as to take ink and transfer it to the surface to be'printed, the underlying portion 'of sald layer being pervious to nloisture and adapted to release it at said s 1n.

8. Transfer mea-ns for offset printing, embodying a layer of material which comprises a colloidal substance and starch; such layer .having its skin treated to render it hard so as to take :ink and transfer it to the surface to be rinted, the underlying portion of said layer eing pervious to moisture and adapted to release it at said skin.

9. Transfer means for offset printing, em-

bodying a layer of a material whlch comprisesa colloidal substance; such vlayer having its skin hardened and grained or matted so as i to take ink and transfer it to the surface to be printed, the underlying portion of said layer being pervious to moisture applied at the back and adapted to release it at said skin. l

10. Transfer means for offset printing, embodying a layer of a material which comrises a colloidal substance; such layer hav- 'mg its skin hardened by treatment with an alkaline bichromate andlight and grained or matted so as to take ink` andtransfer it to the surface to be printed, the underlying portion of said, layer being pervious to moisture applied at the back and adapted to release it at said skin.

11. Transfer means for offset printing,

-embodying a li uid-pervious supporting sheet and a colloldal layer thereon; such layer having its skin treated to render 1t hard so as to take ink and transfer 1t to the surface to be printed, the underlying 

